Help me find this horror movie?

I watched this movie years ago. I remember the beginning started out with two redheaded twin girls,maybe around 11-12,riding a sort of roller coaster thing. Except it looks underground. Imagine the Haunted Mansion ride at Disneyland, it was that type of coaster. Anyway, the girls are laughing at the Halloween decorations, until one looks up and a hand with a rubber glove comes down and covers her mouth and grabs her. The other twin continues laughing at the decorations until she notices her sister is missing. The ride continues and it stops on front of a display of a man dressed like a doctor with a surgical mask and coat. There is a table and something covered with a white cloth. The doctor man rips off the white cloth to reveal the girl who was kidnapped. The doctor then cuts the girls throat. Blood splatters everywhere,including the girls arm which has a watch. The other girl is heard screaming and then it cuts to teens at school. I remember later in the movie a girl is giving a guy a blowjob while he is chained on a wall. As the girls head goes down,we see it come back up guided by a hand because she's decapitated and the guy screams. That's all I remember.